A technique is known for detecting an object upon the surface of a road from an image captured by an image-capturing device that is mounted to a subject vehicle, and for determining its position relative to the subject vehicle.
For example, in the invention described in the cited Patent Reference #1, a technique is described in which, using an image-capturing device mounted to the subject vehicle, images are captured when a strobe is illuminated and when the strobe is not illuminated, and in which a photo-reflective mark is detected by comparing these images together.    Patent Reference #1: Japanese Laid-Open Patent Publication H7-152434.